$\dfrac{7}{5} - \dfrac{4}{8} = {?}$
Solution: $ = {\dfrac{7 \times 8}{5 \times 8}} - {\dfrac{4 \times 5}{8 \times 5}} $ $ = {\dfrac{56}{40}} - {\dfrac{20}{40}} $ $ = \dfrac{{56} - {20}}{40} $ $ = \dfrac{36}{40}$